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Drainage under raised patio that is above DPC - desperate!

4 replies

TodgyCat · 17/05/2020 09:33

Hi,
I've posted before about my a** of a builder, now he's suing me (!) so I'm broke... but I need a practical solution as well as some moral support...

I think I want to drill holes all over the blocks of the block and beam patio, lay our slabs on pedestals that let water drain right through, and pray that the water finds its way safely into the garden. Total patio is 60 sq m, extension is on 30sq m of that, so rain catchment is 30 sq m.

a) is this insane (will the clay below the house turn to mud) and
b) is there anyway we can meet building control?

Builder made a huge mess and invoiced me 90K extra for work he hadn't finished (he had already been paid 80K)... he is now suing me for not paying that 90K...I have spent 30K on lawyers so far. Lawyer expects we will win but builder will then declare insolvency and scarper so I won't get money back.

But even that isn't my issue - although it means delaying my retirement. Am in despair, so looking for some support but also given smart folks here, for practical advice / your experiences. I'll tackle almost anything! But want to be safe and legal.. (ideally... may need to fudge building control). I have engaged 2 surveyors who haven't helped (£2,500...)

Situation: Old victorian house on excellent brick foundations, garden is 6ft below ground floor level, drains 50m down to a lake. Builder built a block and beam patio, on part of which he built a large sunroom (with foundations below the block and beam, which have been inspected). There's a raised bed 3 ft high round the patio, for safety / building regs, with a brick retaining wall on shallow foundations.

  1. The patio hasn't yet been laid and at present there is no drainage (but water barely pools, even in heavy rain). Our old DPC is only 5cm above the current block and beam top - so when we lay slabs it will be above the old DPC. Need to put a french drain in there but the beam is parallel to the old wall and almost touching it - can't remove the beam because the extension is built on top of it.
  1. The extension DPC is 2 bricks higher - so it's almost ok except the front windows and door go below the DPC (!). We plan to rebuild the front and replace the windows so that the door and windows are the correct 2 bricks above the patio - we'll need to fit the patio into max 8cm to achieve this. Again, no hope of fitting a french drain.

Because the patio is so big, any attempt to have a fall across it results in patio being even higher relative to DPC at some point (the beams fix the low point of the patio)... and it can't fall towards the house because we can't fit a drain there because of the beams. Aargh!

Builder lied to building control (a private company) multiple times. We don't yet have a certificate but they were prepared to issue one on basis of his lies. I told them he lied and they didn't answer. Council BC won't talk to us because the private company is dealing with it. Private company has been fairly collaborative but might reasonably walk away at this point. The foundations and insulation have all passed, it's just this drainage issue (and the glass, which we're replacing).

I can usually work problems out somehow, but this has me stumped (likewise various professionals). Letting rain drop through under the patio honestly seems the best option...

Have considered some real Heath Robinson ideas including a tarp under the block and beam to catch rain and direct it out... would have to crawl to fit this!

Please, can anyone help? I'm looking for photos but hope my description is clear....

OP posts:
stairgates · 17/05/2020 09:38

I cant offer any help but feel gutted for you. There should be criminal charges available for these situations. I hope somebody can offer some help.

TodgyCat · 17/05/2020 10:04

@stairgates - Thanks, -- it does help! I am genuinely amazed that you can sue someone for non-payment of invented, disputed invoices. I could add that we now have almost everything exempted from our building insurance, because we have no building certificate. So have to pray nothing else happens.

OP posts:
Inforthelonghaul · 17/05/2020 10:20

Don’t really know much about building controls or drainage but have you thought about making the patio with a resin material which I believe is water permeable? Also I can’t see why you couldn’t have drainage holes too. There must be old houses with this type of issue.

It’s shocking though that you can be doing all this legal stuff, win and still get nothing I thought his liability insurance was for exactly this kind of thing.

TodgyCat · 17/05/2020 10:32

@inforthelonghaul - thanks --- that's about what I'm aiming at, as this way of laying blocks without grout or mortar (on pedestals) means rain goes through the gaps between them, so it is like a very permeable patio... i'm pretty sure building control won't like it but in practice I think it might work.

I found a picture of the foundations which may give an idea -- there is a 4 foot or so void under the patio, which is between the wall in this picture and the moat of concrete (the foundation of the patio support wall)

Drainage under raised patio that is above DPC  - desperate!
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